Significantly lower levels of vitamin D found in NFL players with muscle injuries

A recently presented study of a single National Football League team showed that nearly 81% of players had abnormal vitamin D levels and indicated significantly lower levels among athletes who sustained muscle injuries.

“Vitamin D has many roles,” study investigator Michael K. Shindle, MD, said. “It has been shown to play a role in calcium homeostasis, muscle health and bone health … there is controversy whether peak athletic performance may occur when vitamin D levels are 50 ng/mL or higher. We wanted to look at the prevalence of vitamin D insufficiency in athletes.”

Shindle presented his team’s findings at the 2011 Annual Meeting of the American Orthopaedic Society for Sports Medicine (AOSSM) in San Diego.

Study measures

Shindle and colleagues at the Hospital for Special Surgery in New York hypothesized that vitamin D insufficiency was prevalent among athletes and that players with vitamin D deficiency would have a high rate of muscle injuries. The investigators tested the vitamin D levels of 89 professional football players from a single National Football League team in the spring of 2010. The players had a mean age of 25 years. The researchers requested data from the football team to determine the number of athletes who had lost the ability to play one game or more due to muscle injuries.

The researchers found deficient vitamin D levels in 27 (30.3%) of the players examined. Forty-five players (50.6%) displayed vitamin D levels consistent with insufficiency, while the remaining 17 players displayed vitamin D values described as within normal limits.

Rate of abnormal levels

“There was an alarming percentage — 80.9% of players — with abnormal levels,” Shindle said. “No player had a vitamin D level greater than 50 [ng/mL] … In terms of injury prevention, 18% of players sustained a muscle injury in the previous season. These players all had statistically significant lower vitamin D levels than those players who did not suffer muscular injury.”

Mean vitamin D levels in African-American players were found to be significantly lower than those found in white players, the researchers reported (20.4 ng/mL vs. 30.3 ng/mL, respectively). “Ninety-three percent of African-American players had abnormal levels,” Shindle said.

The 73 players who had no reported muscle injuries were found to have a mean vitamin D level of 24.7 ng/mL, while 16 players with a muscle injury displayed a mean vitamin D level of 19.9 ng/mL.

“Overall, 81% of the team had abnormal vitamin D levels,” Shindle concluded. “African-American players and players that had muscle injury had statistically lower levels. It is still unknown what is the right amount [of vitamin D] for optimal performance. Further studies are warranted to see if there is a correlation with strength and performance testing.”

“Screening and treatment of vitamin D insufficiency in professional athletes may be a simple way to help prevent injuries,” study co-author, Scott A. Rodeo, MD, co-chief of the Sports Medicine and Shoulder Service at the Hospital for Special Surgery and team physician with the New York Giants, stated in an AOSSM press release.

Joseph Lane, MD, a study co-author added, “Further research also needs to be conducted in order to determine if increasing vitamin D leads to improved maximum muscle function,” Lane, who is director of the Metabolic Bone Disease Service at the Hospital for Special Surgery, stated in the release. — by Robert Press

Reference:

• Shindle MK, Voos JE, Gulotta L, et al. Vitamin D status in a professional American football team. Paper #46. Presented at the 2011 Annual Meeting of the American Orthopaedic Society for Sports Medicine. July 7-10. San Diego.
• www.aossm.org

• Michael K. Shindle, MD, can be reached at Summit Medical Group, 1 Diamond Hill Rd, Berkeley Heights, NJ 07922; 908-273-4300; email: mikeshindle@gmail.com.
• Disclosure: The authors have no relevant financial disclosures related to this study.

Champ L. Baker Jr.

The investigators in this interesting study looked at one variable in a study of muscle injuries in players on a single National Football League (NFL) team. What is interesting is the prevalence of insufficient or deficient vitamin D levels in the football players who had lost playing time due to muscle injuries, and the difference in injury rates between black and white players.

Before we can assume, however, that vitamin D deficiency leads to muscle injuries, more needs to be known such as the positions of the players who were injured, the rate of muscle injury in players with normal vitamin D levels and if the muscle injuries in the 16 players were normal for that team.

The question posed by the study’s investigators remains: What is the right level of vitamin D for optimum performance? This study dealt only with a lab finding in muscle injuries in NFL players. Further studies are warranted to follow up on this interesting concept of the association between vitamin D and peak performance and muscle injuries in athletes.

— Champ L. Baker Jr.
Orthopedics Today Editorial Board member
Columbus, Ga.
Disclosure: Baker has no relevant financial disclosures.